Selective nitration of phenol to o-nitrophenol in the presence of metal-free reduced graphene oxide at room temperature

Abstract

We report here a reduced graphene oxide (RGO)-catalyzed ultra-efficient, highly selective and low temperature synthesis of o-nitrophenol using phenol and nitric acid in an equimolar ratio. The effects of various parameters such as concentration of reactants, type of catalyst, weight of the catalyst, solvent, temperature and time of reaction on the catalytic reaction have been explored. The optimum conditions for the catalytic nitration reaction have been observed using a 1 : 1 molar ratio of nitric acid to phenol in the presence of 50 mg RGO in dichloroethane at room temperature for 3 h with a turn over frequency (TOF) of 10.96 × 10¹⁷ molecules g⁻¹ s⁻¹ and a reaction rate of 12.17 × 10¹⁴ molecules mL⁻¹ s⁻¹. In order to explore the decrease in efficiency of the catalyst during reuse, both the parent catalyst and used catalyst have been characterized by XRD, Raman, SEM, EDX, BET and FT-IR. The large surface area of RGO promotes the catalytic activity of aromatic compounds via smooth and high conversion of products with fine regioselectivity. So this protocol opens up a new avenue for the selective synthesis of o-nitrophenol using reduced graphene oxide at room temperature.